(a) Field of the Invention
The invention relates to circuit protection from abnormal surge voltages induced in a shielded cable.
(b) Description of the Prior Art
Various techniques are known for protecting the signal-carrying conductors from noise-induced electrostatic interference, and from lightning-induced electromagnetic interference.
To provide protection to signal wires within the cable from both electrostatic and electromagnetic interferences, the known prior art required two separate, concentric shields, insulated from each other. The outer shield was grounded at both of its end for lightning-induced (electromagnetic), high-voltage interference protection, and the inner shield was grounded only at one end for noise-induced (electrostatic), low-voltage interference protection.
While such a two-shield cable does provide the desired double protection, it can be objectionable in industries wherein weight is a critical factor, as in weight-critical spacecraft or aircraft wiring systems.
Due to critical weight restrictions, some crafts use cables with one-shield grounded only at one end. In such cases, the signal-carrying wires within the cable are susceptible to lightning-induced, relatively-large, wire-to-ground electromagnetic voltages, capable of damaging components within the electronic boxes inter-connected by the one-shield cable.